1. Field of the Invention
The present invention relates to a semiconductor device having a flip chip bonding structure in which a semiconductor chip is bonded to a wiring board with the surface of the semiconductor chip being opposite thereto, and to a semiconductor device having a chip-on-chip structure in which a semiconductor chip is bonded to, as piled up on, the surface of another semiconductor chip. The present invention also relates to a semiconductor chip to be applied to any of the semiconductor devices above-mentioned.
2. Description of Related Art
As a method of improving the density of mounting semiconductor chips on a printed circuit board and of shortening the time required for mounting semiconductor chips, there has been known a so-called flip chip bonding (facedown bonding) in which each semiconductor chip is bonded to the surface of a printed circuit board or the like with the surface of each semiconductor chip facing the surface of the printed circuit board.
In this flip chip bonding structure, a plurality of bumps are disposed on the surface of a semiconductor chip. These bumps are bonded to electrodes disposed on the surface of a wiring board. This not only links the semiconductor chip and the wiring board to each other with a predetermined distance provided therebetween, but also electrically connects the semiconductor chip and the wiring board to each other. The space between the surface of the semiconductor chip and the surface of the wiring board is encapsulated with resin such that the semiconductor chip and the wiring board are housed in a package. This isolates the semiconductor chip from the outside air to prevent the semiconductor chip from being deteriorated in performance by the outside air moisture and the like.
If it is possible to eliminate the step of encapsulating the space between the semiconductor chip and the wiring board with resin, the semiconductor device producing time can be shortened to reduce the production cost of the semiconductor device.
Not only in a semiconductor device having a flip chip bonding structure, but also in a semiconductor device having a chip-on-chip structure in which a semiconductor chip is bonded to, as piled up on, the surface of another semiconductor chip, the space between the semiconductor chips is generally encapsulated with resin to prevent the semiconductor chips from being deteriorated in performance. Accordingly, if it is possible to eliminate the step of encapsulating the space between the semiconductor chips, this can shorten the time required for producing a semiconductor device having a chip-on-chip structure. This can lower the production cost of the semiconductor device.
An arrangement shown in FIG. 4 is adopted when encapsulating a semiconductor device having a chip-on-chip structure with resin. More specifically, one semiconductor chip 91 is bonded to another semiconductor chip 92 in a so-called facedown manner. A plurality of bumps 93 disposed between the semiconductor chips 91, 92, not only link the semiconductor chips 91, 92 to each other with a predetermined distance provided therebetween, but also electrically connect the semiconductor chips 91, 92 to each other. The space between the opposite surfaces of the semiconductor chips 91, 92 is encapsulated with resin 94 to produce a semiconductor module. The semiconductor module thus obtained by encapsulating the space between the semiconductor chips 91, 92 with the resin 94, is further encapsulated with a molding resin 96.
To mate the thermal expansion coefficient of the resin 94 encapsulating the space between the semiconductor chips 91, 92, with that of the semiconductor chips 91, 92, the resin 94 mixingly contains particles (filler) 95 such as silica or the like. This involves the likelihood that the surface protective layers formed at the uppermost surfaces of the semiconductor chips 91, 92 are damaged to deteriorate the performance thereof.
It is a first object of the present invention to provide a semiconductor device which can be produced without requiring resin-encapsulation of the space between a semiconductor chip and the surface of a solid body such as a wiring board or another semiconductor chip, and also to provide a semiconductor chip which can be applied to the semiconductor device above-mentioned.
It is another object of the present invention to provide a semiconductor device capable of preventing the surface of a semiconductor chip from being damaged.
The present invention provides a semiconductor device formed by bonding a semiconductor chip to the surface of a solid body, and this semiconductor device comprises: a connection member disposed between the solid body surface and that surface of the semiconductor chip opposite thereto for supporting the semiconductor chip with a predetermined distance provided between the semiconductor chip and the solid body surface and for electrically connecting the semiconductor chip and the solid body to each other; and an enclosing member which forms, between the solid body surface and that surface of the semiconductor chip opposite thereto, a hollow enclosed space surrounding the connection member.
The solid body surface may be the surface of another semiconductor chip or the surface of a wiring board (e.g., lead frame).
According to the present invention, the enclosing member encloses the space between the surface of the semiconductor chip and the surface of a solid body such as another semiconductor chip or a wiring board. This eliminates the danger of the outside air entering this space. It is therefore not required to encapsulate the space between the solid body and the semiconductor chip with resin to protect the semiconductor chip against the outside air. This shortens the time required for producing the semiconductor device, resulting in reduction in the production cost thereof.
Further, a hollow portion is formed between the surface of the solid body and the surface of the semiconductor chip housed in a package. Accordingly, the surface of the semiconductor chip faces the hollowportion to prevent the surface of the semiconductor chip from being damaged. This eliminates the danger of the semiconductor chip being deteriorated in performance due to damages on the surface thereof.
The space enclosed by the enclosing member may be filled with inert gas. Such an arrangement prevents the semiconductor chip from being deteriorated in performance.
The space enclosed by the enclosing member may be maintained substantially in a vacuum. Such an arrangement not only enhances the adhesion between the solid body surface and the semiconductor chip, but also successfully prevents the outside air from entering this space.
The enclosing member may be an enclosing wall disposed between the solid body surface and the semiconductor chip so as to surround the space there between. The enclosing wall preferably surrounds the connection member on the semiconductor chip surface. Where a plurality of connection members are provided on the surface of the semiconductor chip, all of them are preferably surrounded by the enclosing wall.
When an assembled body formed by bonding the semiconductor chip to the solid body surface with the surface of the semiconductor chip facing the solid body surface, is encapsulated by a resin package, the enclosing member may be an encapsulating resin serving as the material forming the resin package.
Mainly to mate the thermal expansion coefficient of the resin package with that of the semiconductor chip, the encapsulating resin serving as the material of the resin package, often mixingly contains filler particles. In such a case, the filler particle size is preferably greater than the distance between the solid body surface and the surface of the semiconductor chip. This prevents the filler from entering the space between the solid body surface and the surface of the semiconductor chip. This eliminates the danger of the semiconductor chip surface being damaged by the filler in the package material, thereby to further effectively prevent the semiconductor chip from being deteriorated in performance.
When the encapsulating resin mixingly contains a plurality of types of fillers, it is preferable that the particle size of each type of filler is larger than the distance between the solid body surface and the surface of the semiconductor chip and that a filler having a particle size smaller than this distance, is not mixingly contained in the encapsulating resin.
The present invention provides a semiconductor chip to be bonded to the surface of a solid body, and this semiconductor chip comprises: a connection member disposed on that surface of the semiconductor chip opposite to the solid body surface for supporting the semiconductor chip with a predetermined distance provided between the semiconductor chip and the solid body surface and for electrically connecting the semiconductor chip and the solid body to each other; and an enclosing wall disposed around all the circumference of the surface of the semiconductor chip opposite to the solid body surface, this enclosing wall being bonded to the solid body surface for enclosing the space between the surface of the semiconductor chip and the solid body surface.
These and other features, objects and advantages of the present invention will be more fully apparent from the following detailed description set forth below when taken in conjunction with the accompanying drawings.